This invention relates to electrostatic spray coating, and, more particularly, to a nozzle for a powder spray gun which does not require a mechanical powder deflector. In the application of powder coating material to objects in industrial finishing applications, a powder material such as an epoxy, polyester, or porcelain frit is conveyed to an applicator gun by air under pressure, is dispensed from the gun in the form of a spray, and is projected toward the object to be coated in particulate form. As the coating material is dispensed from the gun, the particles are imparted with an electrical charge so that they will be electrostatically attracted toward the object to be coated which is held at electrically ground potential. After coating, the object may be moved into an oven where the powder coating material is baked onto the surface. The material being dispensed from the gun is in particulate form and it is necessary to direct the material in a broadened spray pattern to obtain uniform, smooth and wide coverage of the surface of the object to be coated.
In known electrostatic powder spray guns, a mechanical deflector is mounted at the nozzle end of the gun. The deflector extends into the flow of powder being emitted from the gun and deflects the powder into a conical spray pattern. That is, the deflector is impacted by the powder coating material being emitted from the gun and directs the powder radially outwardly to form a conical spray pattern. As stated above, however, the powder is in particulate form and is characteristically quite abrasive on the parts of the gun impacted by the powder. Moreover, the powder is carried by air under pressure; and, as a result, the effect of the powder on the nozzle parts is much like sandblasting. As a result, mechanical deflectors are subject to rapid wear even though they may be formed of a hard material such as a ceramic. Another problem associated with mechanical deflectors is that the powder impinging on the deflector tends to build up on the surface thereof. After a given amount of buildup, a clump of coating material can drop off and hit the workpiece thereby marring the finish. This is particularly true when the gun is mounted overhead of the workpiece.